An extreme ultraviolet narrow-band high-transmission filter, a preparation method and application thereof

Abstract

The application discloses an extreme ultraviolet narrow-band high-transmittance filter and a preparation method and application thereof. The extreme ultraviolet narrow-band high-transmittance filter comprises a first ruthenium film, a silicon film and a second ruthenium film arranged in sequence from bottom to top. The transmittance of the extreme ultraviolet narrow-band high-transmittance filter is greater than or equal to 32% at a wavelength of 12.3-14.5 nm. Compared with a traditional multilayer film filter, the application has the advantages of simple structure, simple process and high integration on a detector surface, and has a wide application prospect in the field of extreme ultraviolet optics.

Description

Technical Field

[0001] This invention relates to the field of optical technology, specifically to an extreme ultraviolet narrowband high-transmittance filter, its preparation method, and its application. Background Technology

[0002] With the development of semiconductor technology, the reduction of technology nodes in chip manufacturing processes, a standard for measuring chip advancement, is closely related to the reduction of light source wavelength. According to the Rayleigh criterion, technology nodes can be reduced by decreasing the light source wavelength or increasing the numerical aperture. However, since the increase in numerical aperture has almost reached its physical limit, reducing the light source wavelength has been a focus of industry research. Currently, the wavelengths of ultraviolet light sources used have been shortened from the deep ultraviolet (DUV) band to the extreme ultraviolet (EUV) band. This advancement signifies a broader expansion of the applications of ultraviolet light. With its extremely short wavelength and strong penetrating power, extreme ultraviolet light demonstrates enormous potential and value in materials science, biomedical imaging, and spectral analysis.

[0003] The use of extreme ultraviolet (EUV) light sources has facilitated groundbreaking advancements, but it also presents significant challenges. EUV light contains numerous atomic resonance lines, causing absorption of light within a short distance of its propagation through materials. Consequently, multilayer mirrors are currently widely used for spectral filtering in 13.5 nm EUV light. However, it is undeniable that, on the one hand, optical systems containing mirrors require substantial space; on the other hand, based on Bragg's law, the effective layer thickness of the mirror is related to the incident angle of radiation, and its reflectivity fluctuates with the angle of incidence, thus imposing strict limitations on the range of incident angles.

[0004] In extreme ultraviolet (EUV) detector applications, transmission filters exhibit significant advantages, saving space and possessing higher potential application value. Currently, zirconium film filters are widely used due to their high transmittance at 13.5 nm wavelength. However, while they have a response over a relatively wide spectral range (FWHM = 6.2 nm), achieving a sufficiently narrow transmission window remains a challenge. To achieve narrowband filtering, current research indicates that multilayer film structures designed using anomalous transmission effects can generate narrowband transmission peaks at 13.5 nm wavelength. However, this approach faces several limitations. First, the fabrication process for multilayer film structures is complex, requiring high precision in detector fabrication. Second, the relatively low transmittance of multilayer film structures limits the transmission efficiency of EUV light. Third, the radiation incident angle range of multilayer film structures remains limited, affecting their applicability under different incident angle conditions.

[0005] It is worth noting that transmission filters constructed based on the spectral matching method with complementary extinction coefficients possess unique advantages due to the inherent refractive index and absorption edge properties of the material. Over a considerable range of incident angles, the transmission peak of such filters shows almost no significant shift due to changes in the incident angle, and the fabrication process is relatively simple, eliminating the need for extensive thin-film stacking. When integrated into a detector, the main structure can share the core functional parts and electrodes of the detector, solving the problem of electrode shading of the photosensitive part in the detector, significantly reducing fabrication difficulty, and improving device integration. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an extreme ultraviolet (EUV) narrowband high-transmittance filter, its preparation method, and its applications. The EUV narrowband high-transmittance filter of this invention performs specific wavelength filtering on a 13.5 nm EUV light source, allowing only EUV radiation with a wavelength of approximately 13.5 nm to pass through, thus achieving the functions of 13.5 nm narrowband filtering and precise detection.

[0007] To achieve the above objectives, the technical solution designed by the present invention is as follows:

[0008] This invention provides an extreme ultraviolet narrowband high transmittance filter, which includes a first ruthenium thin film arranged sequentially from bottom to top as a contact layer, which has both electrical contact and spectral adjustment functions. It utilizes its absorption characteristics to suppress long-wavelength transmission and construct a long-wavelength cutoff edge for the narrowband spectrum.

[0009] Silicon thin film, as the core filtering layer, utilizes its transmission properties and abrupt extinction coefficient to form a short-wavelength absorption edge in the narrowband spectrum.

[0010] The second ruthenium thin film, as a protective layer, provides a physical and chemical barrier to the silicon thin film. At the same time, it works together with the first ruthenium thin film to form a long-wavelength cutoff edge of the narrow-band spectrum by utilizing its absorption characteristics.

[0011] A sandwich structure is formed by two ruthenium thin films and an intermediate silicon thin film. The short-wavelength absorption edge determined by the silicon thin film and the long-wavelength cutoff edge determined by the ruthenium thin film are superimposed to form a narrow-band transmission spectrum.

[0012] For wavelengths of 12.3–14.5 nm, the transmittance of the extreme ultraviolet narrowband high-transmittance filter is ≥32%.

[0013] Furthermore, at a wavelength of 12.3 nm, the transmittance of the silicon thin film is no higher than 10%, and at a wavelength of 13.5 nm, the transmittance of the silicon thin film is no lower than 75%, and the thickness of the silicon thin film is... d Si Meets the following range:

[0014]

[0015] in, and For wavelength, T κ is the transmittance, and κ is the extinction coefficient;

[0016] At a wavelength of 13.5 nm, the total transmittance of the first ruthenium film (1) and the second ruthenium film (3) is not less than 40%, and at a wavelength of 14.5 nm, the total transmittance of the first ruthenium film (1) and the second ruthenium film (3) is not more than 25%. The total thickness of the first ruthenium film (1) and the second ruthenium film (3) is... d Ru Meets the following range:

[0017]

[0018] in, and For wavelength, T κ is the transmittance, and κ is the extinction coefficient.

[0019] Furthermore, the thickness of the silicon thin film is 150 nm;

[0020] The total thickness of the first ruthenium film and the second ruthenium film is 56 nm.

[0021] The present invention also provides a method for preparing the aforementioned extreme ultraviolet narrow-band high-transmittance filter, the specific process of which is as follows:

[0022] A silicon film and a second ruthenium film are sequentially deposited on the surface of the first ruthenium film using an electron beam evaporation process. After cooling, an extreme ultraviolet narrowband high-transmittance filter can be obtained.

[0023] The present invention also provides an application of the aforementioned extreme ultraviolet narrowband high-transmittance filter in the fabrication of extreme ultraviolet detectors.

[0024] The present invention also provides an extreme ultraviolet detector based on a Schottky barrier photodiode, wherein the extreme ultraviolet detector based on a Schottky barrier photodiode comprises, from bottom to top, a ruthenium ohmic contact layer, an N-type heavily doped 4H-SiC substrate layer, an N-type lightly doped 4H-SiC epitaxial layer and the aforementioned extreme ultraviolet narrowband high transmittance filter.

[0025] The first ruthenium thin film, the lightly doped N-type 4H-SiC epitaxial layer, the heavily doped N-type 4H-SiC substrate layer, and the ruthenium ohmic contact layer in the extreme ultraviolet narrow band high transmittance filter constitute a Schottky barrier 4H-SiC photodiode.

[0026] Furthermore, the doping concentration of the N-type heavily doped 4H-SiC substrate is 10. 18 ~1019 cm -3 ;

[0027] The doping concentration of the N-type lightly doped 4H-SiC epitaxial layer is 1×10⁻⁶. 14 ~3×10 14 cm -3 The thickness of the N-type lightly doped 4H-SiC epitaxial layer is 3~5 μm;

[0028] The thickness of the ruthenium ohmic contact layer is 40~50nm.

[0029] Furthermore, the doping concentration of the N-type heavily doped 4H-SiC substrate is 10. 19 cm -3 ;

[0030] The doping concentration of the N-type lightly doped 4H-SiC epitaxial layer is 1×10⁻⁶. 14 cm -3 The thickness of the N-type lightly doped 4H-SiC epitaxial layer is 4 μm;

[0031] The thickness of the ruthenium ohmic contact layer is 45 nm.

[0032] The present invention also provides an extreme ultraviolet detector based on a PN junction, the extreme ultraviolet detector based on a PN junction comprising, from bottom to top, a ruthenium ohmic contact layer, an N-type heavily doped 4H-SiC substrate layer, an N-type lightly doped 4H-SiC epitaxial layer, a P-type gradient doped 4H-SiC layer, and the aforementioned extreme ultraviolet narrowband high transmittance filter.

[0033] The first ruthenium thin film, the P-type gradient-doped 4H-SiC layer, the N-type lightly doped 4H-SiC epitaxial layer, the N-type heavily doped 4H-SiC substrate layer, and the ruthenium ohmic contact layer in the extreme ultraviolet narrow band high transmittance filter constitute a standard N-type 4H-SiC PN junction photodiode.

[0034] Furthermore, the doping concentration of the N-type heavily doped 4H-SiC substrate is 10. 18 ~10 19 cm -3 ;

[0035] The doping concentration of the N-type lightly doped 4H-SiC epitaxial layer is 1×10⁻⁶. 14 ~3×10 14 cm -3 The thickness of the N-type lightly doped 4H-SiC epitaxial layer is 3~5 μm;

[0036] The doping concentration of the p-type gradient-doped 4H-SiC layer is 1×10⁻⁶ from bottom to top. 16 cm -3 Up to 1×1019 cm -3 The thickness of the p-type gradient-doped 4H-SiC layer is 30~50 nm;

[0037] The thickness of the ruthenium ohmic contact layer is 40~50 nm.

[0038] Furthermore, the doping concentration of the N-type heavily doped 4H-SiC substrate is 10. 19 cm -3 ;

[0039] The doping concentration of the N-type lightly doped 4H-SiC epitaxial layer is 1×10⁻⁶. 14 cm -3 The thickness of the N-type lightly doped 4H-SiC epitaxial layer is 4 μm;

[0040] The thickness of the p-type gradient-doped 4H-SiC layer is 40 nm;

[0041] The thickness of the ruthenium ohmic contact layer is 45 nm.

[0042] The principle of this invention:

[0043] I. The principle of the extreme ultraviolet narrowband transmission filter in this invention is as follows: based on the extinction coefficient characteristics of the material, a spectral matching method with complementary extinction coefficients is used.

[0044] First, the imaginary part of the refractive index of the silicon thin film, i.e., the extinction coefficient, is relatively large in the region with wavelengths less than 12.3 nm. However, around 12.3 nm to 12.4 nm, the imaginary part of the refractive index of the silicon thin film decreases sharply. Therefore, the silicon thin film exhibits a distinct absorption edge in this wavelength range. Based on this inherent optical property, the silicon thin film exhibits good absorption for radiation with wavelengths less than 12.3 nm, while showing good transmission for radiation with wavelengths greater than 12.4 nm.

[0045] On the other hand, when the incident light wavelength increases to 10 nm, the extinction coefficient of the ruthenium thin film begins to show a slow increasing trend with increasing wavelength. Furthermore, this increasing trend becomes more pronounced when the wavelength exceeds 14 nm. Therefore, by rationally controlling the thickness of the ruthenium thin film, the optical properties of the ruthenium thin film in extreme ultraviolet radiation can be adjusted, enabling it to effectively suppress extreme ultraviolet radiation at 14.5 nm and above. Through joint optimization of the extinction coefficients of ruthenium and silicon, along with the thickness, narrowband transmission of radiation near the 13.5 nm wavelength can be achieved. A more detailed theoretical description follows:

[0046] Assuming the light wave used is a plane wave incident normally along the X-axis, its electric field intensity can be expressed as:

[0047]

[0048] In formula (1), the angular frequency is ω wave vector is k Considering , The refractive index , λ 0 is the wavelength in vacuum, therefore:

[0049]

[0050] Substituting equation (2) into equation (1) yields:

[0051]

[0052] Since light intensity is proportional to the square of the electric field strength, light travels at a distance from the material surface... x When light is transmitted through a material, the light intensity satisfies:

[0053]

[0054] in α If the light absorption coefficient is given, then the absorption thickness is... δ It can be represented as:

[0055]

[0056] Record transmittance Then the distance between the transmitted light and the material surface, i.e., the material thickness, is... d material With transmittance T The relationship can be expressed by the following formula:

[0057]

[0058] When designing for silicon thin films, this invention sets forth specific requirements for their thickness: it is expected that the silicon thin film can effectively suppress radiation with wavelengths less than 12.3 nm, ensuring that the transmittance of radiation at a wavelength of 12.3 nm is not higher than 10%; at the same time, it is necessary to ensure that light at a wavelength of 13.5 nm can be highly transmitted and not suppressed, with a transmittance of at least 75%. Given that the extinction coefficients of the silicon thin film at 12.3 nm and 13.5 nm are 0.0168 and 0.00183, respectively, the absorption thickness corresponding to the radiation at wavelengths of 12.3 nm and 13.5 nm can be calculated according to equation (5):

[0059]

[0060] Subsequently, based on the required transmittance conditions mentioned above, the thickness of the silicon thin film is further calculated using formula (6). d SiThe reasonable range for its value is 134 nm to 169 nm.

[0061] Similarly, when designing the ruthenium thin film, this invention also sets specific optical performance requirements: on the one hand, it is necessary to ensure that the transmittance of the two ruthenium thin films at a wavelength of 13.5 nm is not less than 40% to ensure that light at this wavelength can pass through well; on the other hand, the transmittance at a wavelength of 14.5 nm needs to be limited to not exceeding 25% to achieve effective suppression of radiation with wavelengths greater than this. Based on the design requirements, the absorption thickness corresponding to the radiation at wavelengths of 13.5 nm and 14.5 nm is calculated first, respectively.

[0062]

[0063] After obtaining the absorption thickness data for these two wavelengths, and combining the set transmittance conditions, the total thickness of the two ruthenium thin films was determined by formula (6) through further analysis and derivation. d Ru The reasonable range of values ​​is 51.2 nm to 57.5 nm.

[0064] II. The principle of the integrated detector of the present invention is as follows: Based on the characteristics of ruthenium thin film in the fields of optics, electricity and mechanics, the integrated functions of filtering, electrodes and protection are realized.

[0065] First, from an optical perspective, ruthenium thin film, as the core component of the extreme ultraviolet narrowband high-transmittance filter in this invention, exhibits wavelength-selective transmittance of the extreme ultraviolet spectrum due to its extinction coefficient characteristics. Second, from an electrical perspective, based on the work function, ruthenium thin film can form Schottky contacts with both N-type doped 4H-SiC and P-type doped 4H-SiC. Therefore, ruthenium thin film can be directly used as the functional part of the detector. Moreover, when 4H-SiC is heavily doped, ruthenium can form ohmic contacts with the heavily doped semiconductor material. Furthermore, ruthenium itself possesses high electrical conductivity. Therefore, in the two integrated extreme ultraviolet (EUV) detectors of this invention, the ruthenium thin film in contact with the photosensitive area of ​​the SiC detector within the EUV narrow-band high-transmittance filter can be directly used as the detector electrode, eliminating the need for additional electrode fabrication and effectively improving the device's integration density. Moreover, the ruthenium thin film is chemically stable, with a Mohs hardness of 6.5. Therefore, the ruthenium thin film, in direct contact with the air environment, can provide a physical barrier protection for the silicon thin film within the interlayer, significantly enhancing the detector's resistance to damage in complex environments and thus extending its service life. A more detailed theoretical description follows:

[0066] First, in terms of electrical properties, the conductivity of elemental ruthenium is 1.4 × 10⁻⁶. 7 S / m, while nickel electrodes are commonly used in the field of silicon carbide detectors, with a conductivity of 1.43 × 10⁻⁶. 7The S / m values ​​of the two are similar, indicating that ruthenium possesses excellent electrical conductivity and is a suitable electrode material. Secondly, the work function of ruthenium... W m The work function of N-type 4H-SiC is 5 eV. W s The work function of p-type 4H-SiC is approximately 4 eV. W s Typically at 7 eV, when a ruthenium thin film contacts both N-type 4H-SiC and P-type 4H-SiC, a Schottky barrier is formed at the interface of both. Based on this characteristic, in an extreme ultraviolet detector based on a Schottky barrier diode according to the present invention, the ruthenium thin film can directly serve as a Schottky contact layer to contact the lightly doped N-type 4H-SiC, becoming a functional component of the detector; simultaneously, combined with the high conductivity of ruthenium itself, the ruthenium thin film can also simultaneously act as an electrode of the detector, eliminating the need for additional independent electrode structures.

[0067] Furthermore, the ruthenium thin film can form an ohmic contact with the p-type gradient-doped 4H-SiC layer in another PN junction-based detector of this invention. Specifically, when the doping concentration of the p-type 4H-SiC layer used is sufficiently high, charge carriers can penetrate the Schottky barrier through the quantum mechanical tunneling effect, thereby achieving a low-resistance contact.

[0068] Assume the normal vector of the interface between the ruthenium thin film and the p-type gradient-doped 4H-SiC layer is... x Axis, the interface is at x Defined on the axis x = 0, therefore a surface potential exists at the interface. V s The potential barrier height of the hole is qV D ,Right now

[0069]

[0070] To obtain the potential barrier faced by the price band hole, the price band top... E v Choose the zero point of electric potential energy. Let the width of the depletion region be denoted as . d 0, doping concentration is N A When in equilibrium,

[0071]

[0072] in

[0073]

[0074] The potential barrier of a hole is

[0075]

[0076] make y = d 0– x The potential barrier of a hole can be represented as

[0077]

[0078] According to the conclusions of quantum mechanics x = d The probability of a hole at the top of the valence band tunneling through the potential barrier via the tunneling effect is:

[0079]

[0080] When an external voltage is applied, the barrier width is d The surface potential is [( V s )0+ V If ], then the tunnel probability is

[0081]

[0082] As can be seen from equation (15), for a given barrier height, the tunneling probability strongly depends on the doping concentration. N A If the doping concentration is high, the tunneling probability is also high. Integrating the contributions of electrons of various energies to the tunneling current yields the total current, which is directly proportional to the tunneling probability, i.e.,

[0083]

[0084] Define the differential resistance at zero bias as the contact resistance:

[0085]

[0086] Multiplying equation (16) by the contact area, and then using equation (17), we can obtain...

[0087]

[0088] The relationship between contact resistance and doping concentration shown in equation (18) clearly indicates that the higher the doping concentration, the smaller the contact resistance Rc. In this invention, the ruthenium film in the filter is used as the electrode material to form a contact interface with P-type gradient-doped SiC. Because the work function of P-type gradient-doped 4H-SiC is greater than that of the ruthenium film, a hole barrier can be formed at the interface after they come into contact. Moreover, P-type gradient-doped 4H-SiC is defined as having an acceptor doping concentration greater than 10. 19 cm -3Based on this heavy doping condition, the depletion region barrier width is significantly reduced, thereby enabling the ruthenium film to form an ohmic contact with 4H-SiC, with the contact resistance stabilizing at the order of 10. -5 Ω·cm 2 For N-type heavily doped 4H-SiC, the theoretical derivation of its ohmic contact with ruthenium can follow the above approach. Therefore, in the SiC detector structure of this invention, the ruthenium thin film can be directly used as the ohmic contact layer, serving as the ohmic electrode of the detector.

[0089] The beneficial effects of this invention are:

[0090] The sandwich-structured extreme ultraviolet narrowband high-transmittance filter and its integrated detector proposed in this invention have the technical advantage of simplified structure. The processes involved, such as the growth and etching of the thin film materials and the fabrication of the detector, are all relatively mature technologies. By precisely optimizing the thickness parameters of the ruthenium and silicon thin films through a spectral matching method with complementary extinction coefficients, a narrowband pass-through filtering function in the extreme ultraviolet band is achieved, meeting the requirements of extreme ultraviolet transmission filtering detection. Compared with existing technologies, this invention has the following advantages and effects:

[0091] (1) This invention is designed based on the absorption characteristics of silicon and ruthenium thin films. Through the core design concept of "spectral matching method with complementary extinction coefficients", it ensures high transmittance of extreme ultraviolet radiation at the target wavelength of 13.5 nm and efficient suppression of radiation at non-target wavelengths, achieving a narrowband high-transmittance filter with a half-width of 1.5 nm and a transmittance of over 32% at a wavelength of 13.5 nm. Compared with zirconium film transmission filters, it has a narrower bandpass and greater application prospects in fields such as photolithography and materials science.

[0092] (2) Ruthenium possesses stable chemical properties and high Mohs hardness. Compared with silicon and zirconium films, ruthenium films can maintain their metallic properties without significant changes when exposed to oxygen-containing environments, and also have the ability to resist a certain degree of external mechanical damage. Therefore, the filter adopts a sandwich structure, covering both sides of the silicon film with a ruthenium film, which can effectively protect the silicon film physically and effectively avoid the degradation of filtering performance and structural damage caused by oxidation.

[0093] (3) In the two integrated detectors designed in this invention, the inherent characteristics of ruthenium thin films are fully explored and systematically utilized: in the filter structure, it serves as the core functional part to achieve the modulation of the extreme ultraviolet spectrum; in the detector structure based on Schottky barrier diode, it can simultaneously assume the dual functions of Schottky contact layer and electrode; in the detector structure based on PN junction diode, it functions as an ohmic electrode by forming an ohmic contact with semiconductor material. This design architecture ultimately achieves a deep integration of the filter structure and the detector structure, which not only eliminates the need for additional electrode fabrication and effectively simplifies the device fabrication process, but also solves the technical problem of decreased light absorption efficiency caused by electrode coverage of the photosensitive area in traditional detectors from the structural root, while avoiding the drawbacks of material redundancy and excessive structural complexity.

[0094] (4) Traditional multilayer film filters rely on superlattice structure and Bragg effect to achieve filtering. However, according to Bragg's law, changes in the incident angle will cause the center wavelength of the filter to drift, thus affecting the stability of the filtering function. Compared with traditional multilayer film reflective filters, the narrowband filter designed in this paper maintains a relatively stable position of its narrowband transmission peak within the set incident angle range of 0 to 30 degrees. This characteristic can meet the application requirements under different incident angle conditions and greatly expand its application range.

[0095] (5) From the perspective of process cost, the mainstream fabrication processes for optical filters are currently magnetron sputtering or electron beam evaporation (EBE), while the mainstream fabrication processes for extreme ultraviolet detectors include chemical vapor deposition (CVD) and ion implantation. All of these processes are mature industrial fabrication technologies. Specifically, for optical filters, the existing technology based on multilayer film structures requires the stacking and growth of multiple layers of different materials. This not only imposes stringent requirements on the thickness accuracy of each layer, but also requires the replacement of the target material after each layer of material is grown, resulting in a cumbersome fabrication process and high process costs. At the same time, as the number of stacked layers increases, the risk of accumulated thickness error increases significantly, further affecting product yield and cost control. In comparison, the filter proposed in this invention adopts a simplified technical solution. While ensuring the core optical performance such as narrow-band high transmittance in the extreme ultraviolet band, it can significantly simplify the preparation process, reduce the frequency of target material replacement and the risk of thickness error accumulation, thereby significantly reducing process costs and possessing outstanding economic advantages. Attached Figure Description

[0096] Figure 1The graph shows the transmittance of the silicon thin film in the 5-20 nm wavelength region when four different thickness values ​​(i.e., 134.0 nm, 145.7 nm, 157.3 nm, or 169.0 nm) are selected in equal step sizes within the range of 134-169 nm.

[0097] Figure 2 The transmittance of the ruthenium film in the 5–20 nm wavelength region is shown in the figure, with four different thickness values ​​(i.e., thicknesses of 51.2 nm, 53.3 nm, 55.4 nm, or 57.5 nm) selected in equal step manner for a total thickness of 51.2–57.5 nm.

[0098] Figure 3 The figure shows the transmittance of a 150 nm thick silicon thin film in the 5–20 nm wavelength region.

[0099] Figure 4 The figure shows the transmittance of a ruthenium film with a total thickness of 56 nm in the wavelength region of 5 ~ 20 nm.

[0100] Figure 5 This is a schematic diagram of the structure of an extreme ultraviolet narrowband high-transmittance filter.

[0101] Figure 6 This is a schematic diagram illustrating the filtering principle of an extreme ultraviolet narrowband high-transmittance filter.

[0102] Figure 7 The graph shows the transmittance of the extreme ultraviolet narrowband high-transmittance filter in the wavelength region from 5 nm to 20 nm.

[0103] Figure 8 The graph shows the transmittance of the extreme ultraviolet narrowband high-transmittance filter in the wavelength region of 5 nm to 20 nm, corresponding to extreme ultraviolet radiation from an incident angle of 0 to 30 degrees.

[0104] Figure 9 This is a schematic diagram of an extreme ultraviolet detector based on a Schottky barrier photodiode.

[0105] Figure 10 This is a schematic diagram of the filtering principle of an extreme ultraviolet detector based on a Schottky barrier photodiode.

[0106] Figure 11 This is a schematic diagram of an extreme ultraviolet detector based on a PN junction;

[0107] In the figure, 1. First ruthenium thin film; 2. Silicon thin film; 3. Second ruthenium thin film; 4. N-type lightly doped 4H-SiC epitaxial layer; 5. N-type heavily doped 4H-SiC substrate layer; 6. Ruthenium ohmic contact layer; 7. P-type gradient doped 4H-SiC layer;

[0108] Figure 12 This is a schematic diagram of the filtering principle of an extreme ultraviolet detector based on a PN junction. Detailed Implementation

[0109] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can understand it.

[0110] Example 1

[0111] Transmittance Measurement of Ruthenium and Silicon Thin Films

[0112] 1. The transmittance of silicon thin film 2 in the wavelength region of 5-20 nm was measured when the thickness of silicon thin film 2 was 134-169 nm. The results are as follows: Figure 1 As shown, silicon thin film 2 exhibits an absorption edge due to the abrupt change in its extinction coefficient within the wavelength range of 12.3 nm to 12.4 nm. Radiation with wavelengths shorter than 12.3 nm can be effectively absorbed, while radiation with wavelengths longer than 12.4 nm can pass through the silicon thin film. Considering the requirement that the transmittance must meet the following conditions—no more than 10% at 12.3 nm and no less than 75% at 13.5 nm—the thickness of silicon thin film 2 is calculated to be 134–169 nm. Furthermore, the thickness of silicon thin film 2 only affects the magnitude of the transmittance and does not change the position of the absorption edge corresponding to the wavelength.

[0113] 2. The transmittance of the ruthenium film in the 5-20 nm wavelength region was measured when the total thickness of the first ruthenium film 1 and the second ruthenium film 3 was 51.2-57.5 nm. The results are as follows: Figure 2 As shown, since the extinction coefficient of the ruthenium film gradually increases after the wavelength is greater than 10 nm, to ensure that the ruthenium film meets the requirements of a transmittance of not less than 40% at 13.5 nm and a transmittance of not more than 25% at 14.5 nm in practical applications, the total thickness of the first ruthenium film 1 and the second ruthenium film 3 should be 51.2~57.5 nm. Meanwhile, the transmittance spectrum curve within this thickness range shows relatively small and stable variations.

[0114] 3. The transmittance of silicon thin film 2 in the wavelength region of 5–20 nm was measured when the thickness of silicon thin film 2 was 150 nm. The results are as follows: Figure 3 As shown, the silicon thin film 2 achieves a transmittance of 77.5% at 13.5 nm, while the transmittance at 12.3 nm is only 8.2%.

[0115] 4. The transmittance of the ruthenium film in the 5–20 nm wavelength region was measured when the total thickness of the first ruthenium film 1 and the second ruthenium film 3 was 56 nm (the thickness of the first ruthenium film 1 was 30 nm and the thickness of the second ruthenium film 3 was 26 nm). The results are as follows. Figure 4As shown, the ruthenium thin film has a transmittance of 9.9% at 14.5 nm and 40.9% at 13.5 nm, which meets the expected design specifications.

[0116] Example 2

[0117] Extreme ultraviolet narrowband high transmittance filter

[0118] Combination Figure 5 As shown, the extreme ultraviolet narrowband high transmittance filter of this embodiment includes a first ruthenium film 1, a silicon film 2 and a second ruthenium film 3 arranged sequentially from bottom to top.

[0119] The thickness of the first ruthenium thin film 1 is 25~30 nm, the thickness of the silicon thin film 2 is 134~169 nm, the thickness of the second ruthenium thin film 3 is 25~30 nm, and the total thickness of the first ruthenium thin film 1 and the second ruthenium thin film 3 is 51.2~57.5 nm.

[0120] Combination Figure 6 As shown, when broadband extreme ultraviolet incident light irradiates the incident end face of an extreme ultraviolet narrow-band high-transmittance filter, the transmitted extreme ultraviolet radiation is transformed into narrow-band radiation after the synergistic spectral filtering effect of the ruthenium thin film and silicon thin film in the filter, thus realizing the narrow-band filtering function.

[0121] The preparation method of the extreme ultraviolet narrowband high-transmittance filter is as follows:

[0122] A silicon thin film 2 and a second ruthenium thin film 3 are sequentially deposited on the surface of the first ruthenium thin film 1 using an electron beam evaporation process. After the device is cooled to room temperature, an extreme ultraviolet narrowband high-transmittance filter can be obtained.

[0123] Example 3

[0124] Extreme ultraviolet narrowband high transmittance filter

[0125] The extreme ultraviolet narrowband high-transmittance filter in this embodiment is the same as in embodiment 2, except that:

[0126] The thickness of the first ruthenium thin film 1 is 30 nm, the thickness of the silicon thin film 2 is 150 nm, the thickness of the second ruthenium thin film 3 is 26 nm, and the total thickness of the first ruthenium thin film 1 and the second ruthenium thin film 3 is 56 nm.

[0127] Example 4

[0128] Transmittance Measurement of Extreme Ultraviolet Narrow Band High Transmittance Filter

[0129] 1. The transmittance of the extreme ultraviolet narrowband high-transmittance filter of Example 3 in the wavelength region from 5 nm to 20 nm was measured. The results are as follows: Figure 7As shown, the transmission spectrum of the extreme ultraviolet narrowband high-transmittance filter forms a transmission window that meets the requirements at a wavelength of 13.5 nm. In addition, in the wavelength range of 5 nm to 20 nm, the filter does not show any other regions with significant transmittance, and the full width at half maximum (FWHM) is 1.5 nm, which has good narrowband transmission effect.

[0130] 2. The transmittance of the extreme ultraviolet narrowband high-transmittance filter of Example 3 was measured in the wavelength region from 5 nm to 20 nm, corresponding to extreme ultraviolet radiation with an incident angle of 0 to 30 degrees. The results are as follows: Figure 8 As shown, when the incident angle changes within the range of 0 to 30 degrees, the extreme ultraviolet narrowband high-transmittance filter still exhibits good performance characteristics and can maintain the position of the narrowband transmission peak of extreme ultraviolet radiation near the wavelength of 13.5 nm relatively stable.

[0131] Example 5

[0132] Extreme ultraviolet detector based on Schottky barrier photodiode

[0133] Combination Figure 9 As shown, this embodiment provides an extreme ultraviolet (EUV) detector based on a Schottky barrier photodiode, integrating the EUV narrowband high-transmittance filter of this invention. The detector includes, from bottom to top, a ruthenium ohmic contact layer 6, an N-type heavily doped 4H-SiC substrate layer 5, an N-type lightly doped 4H-SiC epitaxial layer 4, and an EUV narrowband high-transmittance filter;

[0134] The second ruthenium film 3 in the extreme ultraviolet narrowband high transmittance filter provides effective physical protection for the silicon film 2. The first ruthenium film 1, the second ruthenium film 3, and the silicon film 2 together play the role of narrowband spectral transmission. The first ruthenium film 1, the lightly doped N-type 4H-SiC epitaxial layer 4, the heavily doped N-type 4H-SiC substrate layer 5, and the ruthenium ohmic contact layer 6 form a Schottky barrier 4H-SiC photodiode. The first ruthenium film 1 simultaneously undertakes the dual functions of forming the Schottky barrier and the electrode.

[0135] Combination Figure 10 As shown, when broadband extreme ultraviolet incident light irradiates an extreme ultraviolet narrow-band high-transmittance filter, the extreme ultraviolet radiation transmitted through the filter is converted into narrow-band radiation, which is then transmitted to a Schottky barrier 4H-SiC photodiode, enabling the detection of a specific extreme ultraviolet band of about 13.5 nm.

[0136] The fabrication method of the extreme ultraviolet detector based on the Schottky barrier photodiode is as follows:

[0137] 1. An N-type lightly doped 4H-SiC epitaxial layer 4 with a thickness of 4 μm was epitaxially grown on an N-type heavily doped 4H-SiC substrate layer 5 (350 μm) using chemical vapor deposition. The doping concentration of the N-type heavily doped 4H-SiC substrate layer 5 was 10. 19 cm -3 The doping concentration of the N-type lightly doped 4H-SiC epitaxial layer 4 is on the order of magnitude 1 × 10⁻⁶. 14 cm -3 The order of magnitude is such that nitrogen is chosen as the N-type dopant.

[0138] 2. Subsequently, on the back side of the N-type heavily doped 4H-SiC substrate layer 5, an electron beam evaporation process is used to deposit a 45 nm thick ruthenium ohmic contact layer 6 to extract current using a high-purity ruthenium target. On the surface of the N-type lightly doped 4H-SiC epitaxial layer 4, an electron beam evaporation process is used to deposit a 30 nm thick first ruthenium thin film 1 to extract current using a high-purity ruthenium target. In this embodiment, the first ruthenium thin film 1 is also used as a Schottky contact layer.

[0139] 3. After deposition, an electron beam evaporation process is used to replace the target material with a high-purity polycrystalline silicon target to locally deposit a silicon thin film 2 with a thickness of 150 nm on the surface of the first ruthenium thin film 1. This deposition method reserves part of the first ruthenium thin film 1 for exposure to meet the electrical connection requirements between the device and the outside world.

[0140] 4. After the silicon thin film 2 is deposited and cooled to room temperature, it is replaced with a high-purity ruthenium target. A second ruthenium thin film 3 with a thickness of 26 nm is deposited on the surface of the silicon thin film 2 as a protective layer using electron beam evaporation. After the sample is cooled to room temperature, the extreme ultraviolet detector based on the Schottky barrier photodiode can be fabricated by taking out the electrode.

[0141] Example 6

[0142] PN junction-based extreme ultraviolet detectors

[0143] Combination Figure 11 As shown, this embodiment provides an extreme ultraviolet (EUV) detector based on a PN junction, integrating the EUV narrowband high-transmittance filter of this invention. The detector includes, from bottom to top, a ruthenium ohmic contact layer 6, an N-type heavily doped 4H-SiC substrate layer 5, an N-type lightly doped 4H-SiC epitaxial layer 4, a P-type gradient-doped 4H-SiC layer 7, and an EUV narrowband high-transmittance filter;

[0144] The second ruthenium film 3 in the extreme ultraviolet narrowband high transmittance filter effectively protects the silicon film 2. The first ruthenium film 1, the second ruthenium film 3, and the silicon film 2 together play the role of narrowband spectral transmission. The first ruthenium film 1, the P-type gradient doped 4H-SiC layer 7, the N-type lightly doped 4H-SiC epitaxial layer 4, the N-type heavily doped 4H-SiC substrate layer 5, and the ruthenium ohmic contact layer 6 form a standard N-type 4H-SiC PN junction photodiode. The first ruthenium film 1 is used as the electrode of the SiC photodetector.

[0145] Combination Figure 12 As shown, when broadband extreme ultraviolet incident light irradiates an extreme ultraviolet narrow-band high-transmittance filter, the extreme ultraviolet radiation transmitted through the filter is converted into narrow-band radiation, which is then transmitted to a standard N-type 4H-SiC PN junction photodiode, enabling the detection of a specific extreme ultraviolet band of about 13.5 nm.

[0146] The fabrication method of the extreme ultraviolet detector based on the PN junction is as follows:

[0147] 1. Using the method in step 1 of Example 5, an N-type lightly doped 4H-SiC epitaxial layer 4 with a thickness of 4 μm is epitaxially grown on the N-type heavily doped 4H-SiC substrate layer 5.

[0148] 2. The detector PN junction is formed on the surface of the lightly doped N-type 4H-SiC epitaxial layer 4 using high-temperature ion implantation technology. Aluminum is selected as the P-type dopant to form a 40 nm thick P-type gradient-doped 4H-SiC layer 7, with a doping concentration of 1×10⁻⁶ from bottom to top. 16 cm -3 Up to 1×10 19 cm -3 After implantation, rapid thermal annealing at high temperature (1800℃) is performed to repair lattice damage caused by implantation and activate the p-type dopant.

[0149] 3. Subsequently, on the back side of the N-type heavily doped 4H-SiC substrate layer 5, an electron beam evaporation process is used to deposit a 45 nm thick ruthenium ohmic contact layer 6 to draw out current using a high-purity ruthenium target. On the surface of the P-type gradient doped 4H-SiC layer 7, an electron beam evaporation process is used to deposit a 30 nm thick first ruthenium thin film 1 to draw out current using a high-purity ruthenium target. In this embodiment, the first ruthenium thin film 1 is also used as a ruthenium ohmic contact layer.

[0150] 4. The steps of depositing silicon thin film 2 and second ruthenium thin film 3 are the same as steps 3 and 4 in Example 5. The electrodes are then led out to complete the fabrication of the extreme ultraviolet detector based on the PN junction.

[0151] All other parts not described in detail are existing technologies. Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An extreme ultraviolet narrow-band high-transmission filter, characterized by: The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; a silicon thin film (2) as a core filter layer, which uses its transmission characteristics and extinction coefficient mutation to form a short-wave absorption edge of a narrow-band spectrum; a second ruthenium thin film (3) as a protective layer, which provides a physical and chemical barrier for the silicon thin film (2) and, together with the first ruthenium thin film (1), uses its absorption characteristics to form a long-wave cutoff edge of a narrow-band spectrum; The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; The transmittance of the silicon thin film (2) is not higher than 10% at a wavelength of 12.3 nm, and the transmittance of the silicon thin film (2) is not lower than 75% at a wavelength of 13.5 nm, the thickness of the silicon thin film (2) d Si satisfies the following range: wherein and is the wavelength, T is the transmittance, and k is the extinction coefficient; The total transmittance of the first ruthenium thin film (1) and the second ruthenium thin film (3) is not less than 40% at a wavelength of 13.5 nm, and the total transmittance of the first ruthenium thin film (1) and the second ruthenium thin film (3) is not more than 25% at a wavelength of 14.5 nm, and the total thickness of the first ruthenium thin film (1) and the second ruthenium thin film (3) is not more than 1 nm d Ru satisfies the following range: wherein and is the wavelength, T is the transmittance, and k is the extinction coefficient.

2. The EUV narrow-band high-transmission filter according to claim 1, characterized in that: The thickness of the silicon thin film (2) is 150 nm; The total thickness of the first ruthenium thin film (1) and the second ruthenium thin film (3) is 56 nm.

3. The use of an extreme ultraviolet narrow-band high-transmission filter in the manufacture of an extreme ultraviolet detector, characterized in that: The extreme ultraviolet narrow-band high-transmittance filter is the extreme ultraviolet narrow-band high-transmittance filter according to any one of claims 1-2.

4. A Schottky barrier photodiode based extreme ultraviolet detector, characterized by: The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; 5. The Schottky barrier photodiode based EUV detector of claim 4, wherein: The N-type heavily doped 4H-SiC substrate layer (5) has a doping concentration of 10 18 ~10 19 cm -3 ; The doping concentration of the lightly doped N-type 4H-SiC epitaxial layer (4) is 1×10⁻⁶. 14 ~3×10 14 cm -3 The thickness of the N-type lightly doped 4H-SiC epitaxial layer (4) is 3~5 μm; The thickness of the ruthenium ohmic contact layer (6) is 40-50 nm.

6. The Schottky barrier photodiode based EUV detector of claim 5, wherein: The N-type heavily doped 4H-SiC substrate layer (5) has a doping concentration of 10 19 cm -3 ; The N-type lightly doped 4H-SiC epitaxial layer (4) has a doping concentration of 1 x 10 14 cm -3 -3 and a thickness of 4 μm. The thickness of the ruthenium ohmic contact layer (6) is 45 nm.

7. A PN-junction based extreme ultraviolet detector, characterized by: The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; The extreme ultraviolet narrow-band high-transmittance filter comprises, from bottom to top, a first ruthenium thin film (1) as a contact layer, which has the functions of electrical contact and spectrum adjustment, and uses its absorption characteristics to inhibit long-wave transmission and construct a long-wave cutoff edge of a narrow-band spectrum; 8. The PN-junction based EUV detector of claim 7, wherein: The N-type heavily doped 4H-SiC substrate layer (5) has a doping concentration of 10 18 ~10 19 cm -3 ; The doping concentration of the N-type lightly doped 4H-SiC epitaxial layer (4) is 1×10 14 cm 14 -3×10 -3 The thickness of the N-type lightly doped 4H-SiC epitaxial layer (4) is 3-5 μm. The doping concentration of the P-type gradient-doped 4H-SiC layer (7) is 1×10 16 cm -3 to 1×10 19 cm -3 from bottom to top, and the thickness of the P-type gradient-doped 4H-SiC layer (7) is 30-50 nm; The thickness of the ruthenium ohmic contact layer (6) is 40-50 nm.

9. The PN-junction based EUV detector of claim 8, wherein: The N-type heavily doped 4H-SiC substrate layer (5) has a doping concentration of 10 19 cm -3 ; The N-type lightly doped 4H-SiC epitaxial layer (4) has a doping concentration of 1 x 1014cm-2 14 cm -3 -2, and a thickness of 4 μm. The thickness of the P-type gradient-doped 4H-SiC layer (7) is 40 nm; The thickness of the ruthenium ohmic contact layer (6) is 45 nm.

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